Several clinical conditions require close monitoring of respiratory activity including respiratory failure, respiratory tract infections as well as respiratory depression associated with anesthesia and sedatives. Also, respiratory disorders are known to disturb sleep patterns. For example, recurrent apneas and hypopnea lead to intermittent hypoxia that provokes arousals and fragmentation of sleep, which in turn may lead to restless sleep, and excessive daytime sleepiness. Repetitive apneas and intermittent hypoxia may also elicit sympathetic nervous system activation, oxidative stress and elaboration of inflammatory mediators which may cause repetitive surges in blood pressure at night and increase the risk of developing daytime hypertension, atherosclerosis, heart failure, and stroke independently from other risks.
There remains a need for improved tools and methods for monitoring respiratory activity, for example in a clinical setting, or again in diagnosing and/or monitoring respiratory disorders, as discussed above, in order to reduce or even obviate the risks that may be associated therewith.
Namely, while some have proposed diagnostic tools and methods for diagnosing, monitoring and/or generally investigating certain breathing disorders, these tools and methods are often particularly invasive and/or uncomfortable for the subject at hand, and therefore, can yield unsatisfactory results. For instance, many diagnostic procedures are solely implemented within a clinical environment, which amongst other deficiencies, do not allow for monitoring a subject in its natural environment, leading to skewed or inaccurate results, or in the least, forcing the subject through an unpleasant and mostly uncomfortable experience.
Alternatively, different portable devices have been suggested for the diagnosis of sleep apneas; however, these solutions generally require the subject to position and attach several wired electrodes themselves in the absence of a health care provider. Unfortunately, subject-driven electrode positioning and installation often leads to a reduction in subject comfort and compliance, and increases the chance that the electrodes will be detached or displaced in use. Since accurate positioning and installation of such electrodes are paramount to proper diagnostics, captured signals in such situations are often unreliable, a measure which can only effectively be determined once the data is transferred back to a health center, at which point, such data, if properly identified, must be withdrawn from the study. Furthermore, such devices regularly need to be shipped back to the health center for processing and, given their generally invasive nature, for hygienic reconditioning, e.g. disinfection.
Similarly, in a clinical setting, while the positioning and attachment of monitoring electrodes may be completed by an experienced health care professional, the devices currently used in such settings generally at best leave the subject physically wired to one or more monitoring devices, if not via more invasive techniques, which wiring can be a particular nuisance to the subjects general comfort and mobility, and obtrusive to individuals or health care practitioners maneuvering around the subject. For example, International Application Publication No. WO 01/15602 describes a clinical system wherein a microphone is suspended from the ceiling above the subject, the recorded data of which is combined with readings from an esophageal pressure catheter and nasal airflow monitoring.
Less intrusive methods have been proposed, for example in U.S. Pat. No. 5,797,852, wherein a microphone is suspended from a base device sitting on the headboard of the subject's bed to record sound produced by the subject's breathing, which base device further comprises a second microphone to record ambient noise in the subject's room. Clearly, the accuracy of the recordings is highly dependent on the subject's position, which will most likely vary during a given sleeping period. Other examples found in U.S. Pat. No. 6,142,950 and US Patent Application Publication No. 2002/0123699 provide facially mounted devices configured for either airflow or sound recordal, respectively. While these latter devices may be less dependent on subject positioning, they are equally limited in the type of data acquired for processing, as only one of airflow or sound can be accessed by any one of these designs. Similarly, International Application Publication No. WO 2006/008745 describes the use of a standard headset having a microphone disposed in front of the subject's mouth to monitor expiratory airflow, with other subject driven and ambient sounds being expressly filtered out as parasitical to the intended system. Furthermore, each of the above examples proposes a configurationally limited design that generally suffers from various deficiencies which, in operation, limit its effectiveness in capturing accurate and usable data.
Accordingly, there is a need for a new mask and method for use in respiratory monitoring and/or diagnostics that overcome some of the drawbacks of known techniques, or at least, that provide the public with a useful alternative. Furthermore, improvements and/or alternative approaches in the type and quality of information collected in monitoring and/or diagnosing a subject, as well as in the methods and procedures implemented in processing and analyzing this information are needed to yield better results without, for example, necessarily requiring further data diversity which, ultimately, can result in greater constraints to the subject's mobility and/or comfort.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.